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Old 10-01-2020, 01:57 PM   #1
1930-Pickup
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Join Date: Mar 2017
Location: southern California
Posts: 725
Default Fuel Line, Shut-Off Valve to Firewall: Why Made Of Hard Steel?

This is a tech-heavy post dealing with material harnesses and the manufacturing process of fuel lines. This is a heads-up if you're not into that.

I'm working on a fuel shut-off valve project and this question came up.

Does someone know why the fuel line that runs from the gas tank shut-off valve to the firewall (fuel strainer) is made from hard steel?

Typically, the main material hardness options for most types of fluid lines are:
1. Aluminum (soft and hard)
2. Copper (soft and hard)
3. Carbon steel (soft, half-hard, and hard).
4. Stainless steel (varying hardness).

Most car manufacturers stay away from aluminum and copper for fuel lines. In vibrating environments, these materials may work-harden over time, then fatigue and crack.

Based on working (cutting, bending, flaring) with a repop Model A fuel line, it seems to be made from hardened steel. Why hard steel?

The original (seamed) Model A fuel line is also hard.

The first thing I thought of was that there may have been concern that the fuel line may be damaged by the passengers feet. This is possible of course, but the fuel line is fairly high up and mostly out of the way, in my opinion anyway.

If these fuel lines were to be made of annealed (soft) steel instead of hard steel, they would be easier to fabricate, and they would still hold their shape very well over the short distance that these lines run. An annealed steel fuel line would also be easier to install since the tube could then be 'tweaked' into place without specialty tools. Not easy to do with the hard steel line that acts like a spring. So why not annealed steel?

For your reference, most auto parts stores sell annealed steel straight tubes (with flares at each end) for fabricating your own fuel and brake lines.

Its my belief that the original seamed tubes were mostly processed while hot; the seam sealing process required that of course. Tube cutting, bending, and flaring may have also been performed hot. Then the tubes would have been quenched for quicker processing. Through that whole process, the tube material became hardened. I believe the hardness of the original tubes was a RESULT of the manufacturing process, and it was not deliberately hardened. I have no facts to support that this is how the tubes were made, but its logical I think.

When the repop manufacturers reproduced Ford's fuel line, its reasonable to assume that they would have copied as much as possible (including the hardness). However, the modern fuel tubes don't have a seam...the 'seam' process of manufacturing tubes is obsolete. It seems that the repop tubes are hard, but they don't need to be.

I'm looking for input. I made several assumptions which I cannot substantiate.

Is there any reason to not make the fuel lines from annealed steel?

Thanks for your support!
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Last edited by 1930-Pickup; 10-05-2020 at 01:01 PM.
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